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Showing papers in "Canadian Electrical Engineering Journal in 1983"


Journal ArticleDOI
TL;DR: One way of considering the problem of generating unit maintenance scheduling is to levelize the amount of reserve throughout the year and this approach is designed as the risk levelization technique.
Abstract: Consideration of maintenance scheduling of generating units is an important aspect in the development of an optimum generation system expansion plan. This consideration will become even more important as the move towards large fossil and nuclear units continues. Maintenance scheduling should permit the required work to be accomplished but not create excessive risk to the system. The problem can therefore be considered in terms of levelizing the system risk throughout the year and this approach is designed as the risk levelization technique. Another way of considering the problem of generating unit maintenance scheduling is to levelize the amount of reserve throughout the year. This technique therefore, is, designated as the reserve-levelizing approach. Both techniques are used in this paper and a comparison between them is presented. The effect on maintenance scheduling of changing the system hourly peak demands and the availability of generating units have been studied and are also presented. These studies are based on the Gram Charlier series of Edgeworth Form.

11 citations


Journal ArticleDOI
TL;DR: In this paper, the rotor flux orientation of field oriented induction motors is used to evaluate the response of a CIVSI-fed induction motor to a step change in load torque and speed.
Abstract: The field oriented controlled induction motor is found to have a good dynamic performance that is comparable to a separately excited DC motor. This paper discusses the advantages of current impressed voltage source inverter (CIVSI) fed induction motor based on rotor flux orientation. The digital simulation results of the scheme and the experimental waveforms are presented. The response of the system for a step change in load torque and step change in speed are studied. The system is found to have a fast dynamic response and better accuracy.

10 citations


Journal ArticleDOI
TL;DR: In this article, an integrated acousto-optic receiver (spectrum analyzer) was developed, which employs three tilted, uniform transducers to provide a 3 dB operating bandwidth of 141 MHz centered at 151 MHz.
Abstract: Various measurements pertinent to the development of an integrated acousto-optic receiver (spectrum analyzer) are considered. The developed receiver employs three tilted, uniform transducers to provide a 3 dB operating bandwidth of 141 MHz centered at 151 MHz. The three elements were phased acoustically eliminating the need for electrical phase matching networks. The receiver utilizes external optics, and has Rayleigh criterion resolution of 2 MHz.

9 citations


Journal ArticleDOI
TL;DR: In this paper, a self-tuning PID digital voltage regulator for a synchronous generator is presented. But the PID control algorithm is dynamically changed according to the estimated model and a second control strategy comprising a dynamic variation of the weighting coefficients of the main and stabilizing feedback signals is also described.
Abstract: A computer study of self-tuning PID digital voltage regulator for a synchronous generator is presented. The regulator is simple and can handle regular load changes as well as severe disturbances in the power system. The algorithm for the proposed regulator combines a least-squares estimator with a digital PID control algorithm. The parameters of the PID control algorithm are dynamically changed according to the estimated model. A second control strategy comprising a dynamic variation of the weighting coefficients of the main and stabilizing feedback signals is also described. The influence of the PID regulator with one of the two control strategies applied at a time, and with the two of them simultaneously applied are examined for various disturbances. Compared to a conventional continuous acting voltage regulator, the proposed regulator improves the transient performance of the synchronous machine.

7 citations


Journal ArticleDOI
TL;DR: In this article, an equivalent circuit for axial and eddy currents in lossy cores has been proposed, which represents the distributed nature of the coupling mechanism between the coil and the core by simple lumped elements.
Abstract: When an induction coil surrounds a lossy core so that there is a gap between coil and core, heating of the core takes place by both axial currents and circumferential eddy currents. An equivalent circuit supported by experimental evidence has been devised for this induction coil-lossy core configuration which represents the distributed nature of the coupling mechanism between the coil and the core by simple lumped elements. While induction heating has traditionally been represented by lumped equivalent circuits, such circuits do not account for axial currents which are invariably the dominant source of heating in cores of low conductivity. The proposed equivalent circuit predicts the relative magnitudes of both axial and eddy current heating for virtually any core conductivity.

6 citations


Journal ArticleDOI
TL;DR: In this article, a harmonic current's compensation method suitable for an electrical distribution system is described, which involves the operation of a harmonic currents generator in parallel with the nonlinear loads and the distribution system.
Abstract: A harmonic current's compensation method suitable for an electrical distribution system is described. The compensation method involves the operation of a harmonic currents generator in parallel with the nonlinear loads and the distribution system. The controlled harmonic current's source is realized using a power transistor inverter. Computer-aided simulation and experimental results obtained in the case of a single phase compensator scheme confirm the validity of the proposed method.

4 citations


Journal ArticleDOI
TL;DR: In this paper, a modification of the feedpoint and backplane cavity which suppresses normal mode generation is required to affect the lower bandedge anomalies, unlike those which occur at the upper bandedge, cannot be controlled by front-edge tapering.
Abstract: Swept-frequency radiation patterns for several helical antennas indicate that both the lower and upper edges of the passband are marked by the occurrence of a series of anomalies responses which are characterized by very narrow band fluctuations in the swept-frequency gain and axial ratio plots. The upper bandedge gain anomalies coincide with the reflection coefficient and axial ratio variations reported in the literature. The occurrence of both the upper and lower bandedge anomalies is shown to be related to two mode stop regions in the helix dispersion diagram. Several suggested tapering schemes have been tested and it is shown that the lower bandedge anomalies, unlike those which occur at the upper bandedge, cannot be controlled by front-edge tapering. A modification of the feedpoint and backplane cavity which suppresses normal-mode generation is required to affect the lower bandedge anomalies.

4 citations


Journal ArticleDOI
TL;DR: Single and multi-level thresholding schemes are applied to images of industrial parts and the results are presented to show how the defects can be detected using image processing techniques.
Abstract: Thresholding of a given image into a binary one is a necessary step for most image analysis techniques. Different thresholding techniques have been proposed in the literature to achieve this goal. In this work the authors investigate some of the available techniques, and examine their suitability for industrial applications, such as on-line quality inspection. Single and multi-level thresholding schemes are applied to images of industrial parts and the results are presented. In addition, examples are given to show how the defects can be detected using image processing techniques.

3 citations


Journal ArticleDOI
TL;DR: A new method is discussed based on a second order model and a simple iterative computational procedure that has been applied to a test network and compared with corresponding results using the linearized technique.
Abstract: Present techniques in stochastic load flow analysis are discussed briefly. High variances of the random variables are usually encountered. The most practical stochastic load flow method which is based upon the least squares estimation technique suffers from the assumption that a linearized model can be used. A new method is discussed based on a second order model and a simple iterative computational procedure. The new algorithm has been applied to a test network. Results are presented and compared with corresponding results using the linearized technique.

3 citations


Journal ArticleDOI
TL;DR: In this article, a minimax approach to the design of 2D FIR digital filters is given, which utilizes the well-known Fourier series method in conjunction with Kaiser window.
Abstract: A minimax approach to the design of 2-D FIR digital filters is given. This method utilizes the well-known Fourier series method in conjunction with Kaiser window. A suitable non-linear optimization method for calculating the parameter α of the Kaiser window is used in order to minimize the maximum of error in the passband and stopband of the filter. This technique provides some improvement over the straightforward approach whereby α is calculated by the empirical formula of Kaiser. To illustrate the method, several examples of 2-D lowpass FIR digital filters with circular and rectangular cut-off boundary are given.

2 citations


Journal ArticleDOI
TL;DR: A network-theoretic approach for counting the number of spanning trees of a graph based on a theorem in the theory of determinants, which results in a recurrence relation for counting Γn, the numberof spanning trees in a multigraph ladder having (n+1) nodes, is established.
Abstract: A network-theoretic approach for counting the number of spanning trees of a graph is proposed. This approach is based on a theorem in the theory of determinants. Following this approach, a recurrence relation for counting Γn, the number of spanning trees in a multigraph ladder having (n+1) nodes, is established. A recurrence relation is obtained connecting the sequences {Wn} and {Γn} where Wn is the number of spanning trees in a multigraph wheel having (n+1) nodes. The significance of the approach is further illustrated by giving simple proofs of certain well-known results, in particular, the formula for counting the number of spanning trees in a cascade of 2-port networks.

Journal ArticleDOI
TL;DR: In this paper, a common configuration for such an array is achieved by connecting the centres of the linear elements by a single structural member such that the reflector is an array of parasitic dipoles excited by a driven element located in front of a reflector.
Abstract: Arrays of finite conducting linear elements are often used to approximate solid reflectors in applications where weight and wind loading make it impractical to use large, solid surfaces A common configuration for such an array is achieved by simply connecting the centres of the linear elements by a single structural member such that the reflector is an array of parasitic dipoles excited by a driven element located in front of the reflector Theoretical and experimental data obtained for several plane, corner and parabolic reflector configurations show that distinct resonances, characterized by narrowband fluctuations in the radiation pattern may seriously affect the operation of these antennas Adjustment of the reflector element length and spacing provides an effective means of controlling these resonances

Journal ArticleDOI
TL;DR: In this paper, the fundamental numerical techniques used to calculate the amplitude probability distribution (APD) of nonGaussian electromagnetic noise envelopes are summarized with special emphasis placed on the interpretation of the physical meaning of the descriptive parameters.
Abstract: The fundamental numerical techniques used to calculate the amplitude probability distribution (APD) of nonGaussian electromagnetic noise envelopes are summarized with special emphasis placed on the interpretation of the physical meaning of the descriptive parameters. In particular, the Middleton physicostatistical models, which can be used for noise of class A as well as class B (narrow band or wide band noise) are fully studied in view that original numerical results can facilitate the interpretation of most statistical parameters. A set of significant results then shows that it is possible to predict the behaviour of a noisy environment through an analysis of the different curves obtained numerically.

Journal ArticleDOI
TL;DR: The purpose of this article has been limited to presenting original speech coding methods which may prove interesting for specific applications, in the light of preliminary results.
Abstract: The great design simplicity of `delta modulators' has indicated a considerable development potential for this technique. However, at a very slow rate of delivery, the quality achieved deteriorates considerably to the extent of limiting the use of delta modulation to a few very specialized functions. Based on extremely simple delta modulators, some speech signal processing methods have nevertheless shown satisfactory results. These methods are described and call for separate processings (alternate or joint) of the signal sign and envelope and, in a more performing version, a variable frequency sampling of the rectified envelope. For channel processing, the transmission is achieved at the fixed rate of 8 Kbit/s. Moreover, in order to reduce digital computations, the delta coding of a speech signal digitized after a logarithmic compression of voice modulated amplitude is considered on the basis of previous methods. The purpose of this article has been limited to presenting original speech coding methods which may prove interesting for specific applications, in the light of preliminary results.

Journal ArticleDOI
TL;DR: In this paper, a two-stage DC to AC inverter configuration for up to 3 kVA power applications is described, where the main advantage over typical inverter configurations is the drastic size (and weight) reduction of its magnetic components.
Abstract: A novel two stage DC to AC inverter configuration intended for up to 3 kVA power applications is described in this paper. Its main advantage over typical inverter configurations is the drastic size (and weight) reduction of its magnetic components. Furthermore, the proposed inverter offers high operating efficiency, programmable output frequency, small overall size and weight and, finally, improved reliability.

Journal ArticleDOI
TL;DR: A new entropy power factor is defined which expresses the change in entropy associated with the sequential redundancy alone and is used to calculate the information transmission rate of a signal ensemble with a given autocovariance function.
Abstract: The change in entropy of an ergodic signal ensemble that passes through a linear discrete filter is written in terms of the z-transform transfer function of the system and expressed as the entropy power factor of the filter. The entropy change in the first order continuous amplitude distribution is separated from the sequential component that results from the effect of the system on the correlation function and power spectrum of the ensemble. A new entropy power factor is defined which expresses the change in entropy associated with the sequential redundancy alone. The results are used to calculate the information transmission rate of a signal ensemble with a given autocovariance function.

Journal ArticleDOI
TL;DR: In this article, the economic dispatch conditions of a power system are evaluated using a rearranged active-reactive power loss model, which is divided into two separate submodels, and the constrained fuel cost function is then minimized to obtain the economic dispatching solutions of the power system under consideration.
Abstract: The economic dispatch conditions of a power system are evaluated using a rearranged active-reactive power loss model. The active-reactive power loss model is divided into two separate submodels. In this formulation, the network total active and reactive power losses are expressed in terms of the active and reactive powers of the generation buses. The network purely reactive sources are modeled in terms of the total reactive load demand. The advantages gained by this separation are discussed. The parameters of the network submodels are estimated by least squares with a high degree of accuracy from a set of load flow results. Based on the above submodels, the constrained fuel cost function is then minimized to obtain the economic dispatch solutions of the power system under consideration. Results are presented for a standard IEEE test system for a wide range of system load levels. The results obtained by the proposed method are also compared to the economic dispatch solutions based on the active power loss model.

Journal ArticleDOI
TL;DR: In this article, a relation between the E-set associated with n-points and floating axis associated with homogeneous positive real functions has been established, and a few associated properties have also been discussed.
Abstract: A relation between the E-set associated with n-points and floating axis associated with homogeneous positive real functions has been established. A few associated properties have also been discussed.

Journal ArticleDOI
A. Semlyen1
TL;DR: In this paper, a geometrical representation of the cost function by ellipsoids in the multi-dimensional space of generator powers is presented, where the power balance or load flow constraints are represented by a hypersurface and the optimum results as the point of tangency of these surfaces.
Abstract: The economic scheduling of generation in power systems was traditionally performed by solving the equations of coordination while satisfying the constraint of power balance between load and total generation. Later, optimal load flow programs were developed to take into account generator voltages as control variables and different operational constraints. There is continuing interest in developing and improving these techniques. The present paper gives a unifying view of the above problems by a geometrical representation of the cost function by ellipsoids in the multi-dimensional space of generator powers. The power balance or load flow constraints are represented by a hypersurface and the optimum results as the point of tangency of these surfaces. The conclusions consist of recommendations for efficient computation of optimal load flows.

Journal ArticleDOI
TL;DR: In this article, the authors present the analysis done on 27 years of meteorologic datas provided by Environment Canada by using extensive computer calculations, the following results are produced: typical curves of hourly average temperature given on a daily, monthly or yearly basis, spectral representations of daily average temperature and daily amplitude, and some observations about the lack of weather prediction using degree-days.
Abstract: Energy storage and management systems require the best possible forecast regarding temperature behavior Heating depends almost directly on outside temperature and cost to Canadian people as much as 20% of energy resources The following paper presents the analysis done on 27 years of meteorologic datas provided by Environment Canada By using extensive computer calculations, the following results are produced: typical curves of hourly average temperature given on a daily, monthly or yearly basis, spectral representations of daily average temperature and daily amplitude, and some observations about the lack of weather prediction using degree-days The analysis show how a digital temperature generator can be implemented with a limited size data memory

Journal ArticleDOI
A. Pomerleau1
TL;DR: A new approach for the reduction of the number of mathematical operations and the amount of memory required for two dimensional Fast Fourier Transforms based on the restriction that the input data is real is presented.
Abstract: Presents a new approach for the reduction of the number of mathematical operations and the amount of memory required for two dimensional Fast Fourier Transforms. The approach, developed to support special purpose high speed hardware, is based on the restriction that the input data is real. It leads to a reduction in the number of mathematical operations for both one and two dimensional transforms. The new representation of the spectrum requires half the amount of memory used in the conventional representations. Filtering though it requires the same amount of calculations, needs some interpretation and some relations had to be developed to relate the spectrum of the filtered image to the filter and the original image.